Method for preparing concentrated and emulsions calibrated in a highly viscous phase, in particular bitumen emulsions

ABSTRACT

A process provides a stable emulsion, in particularly a stable, concentrated bitumen emulsion, by emulsifying a first hydrophobic or hydrophilic phase having a viscosity between 1 and 5000 Pa.s with a second phase immiscible in the first phase, in the presence of at least one surfactant, by mixing together the first phase, second phase, and surfactant under a laminar shear regime.

This application is a 371 of PCT/FR 98/01674 filed Jul. 28, 1998.

The present invention relates to a process for emulsifying a viscoushydrophobic or hydrophilic phase, which is useful in particular forpreparing concentrated and calibrated bitumen emulsions, and alsorelates to the emulsions thus obtained.

Emulsions concentrated in highly viscous hydrophobic compound(s) areused in particular in the surfacings sector, such as, for example, inthe road industry. The reason for this is that emulsions represent anattractive alternative to the problem of spreading bitumen on roadsurfaces. In the traditional technique, the pure bitumen is used hot,which works out to be expensive and can be hazardous for the worksitepersonnel. When the bitumen is emulsified in water, the materialobtained is entirely fluid at room temperature, thus allowing it to beused without difficulty. Under the effect of the evaporation anddrainage of the water, a homogenous bitumen film is obtained after a fewhours. Emulsions concentrated in highly viscous hydrophobic compoundsare also used in the adhesives industry via bonding agents made withemulsion based on colophony esters. For their part, emulsionsconcentrated in viscous hydrophilic compound(s) are more particularlyused in the pharmaceutical and food industries.

However, the techniques available at the present time for preparingemulsions of this type in most cases require high temperatures, highpressures and/or high shear rates.

Thus, if we consider the specific case of bitumen, the correspondingemulsions are currently prepared by hot injection. In general, thebitumen is heated to a temperature above 120° C. and the continuousphase, generally water, is heated to about 60° C. The mixture of bitumenand the aqueous phase is injected into a turbomixer with a very highstirring speed, of about 5000 rpm, and under a pressure which can be upto 3 atmospheres. After such a treatment, bitumen emulsions having abitumen concentration not exceeding 70% by weight of bitumen, a largeaverage droplet size (typically greater than 5 microns) and apolydispersity which is also large are generally obtained.

This type of process thus has several drawbacks.

In particular, conventional processes do not make it possible to prepareemulsions with a bitumen concentration of more than 70%. However,certain specific applications require, as regards the handling of theemulsions, emulsions with bitumen concentrations of more than 90%. Thisis the case, for example, for the mastics used for leakproofing work(protection of buildings, pipelines and the undercarriage of cars).

Finally, the bitumen emulsions currently available are not satisfactoryin terms of monodispersity. The size of the bitumen droplets present inthese emulsions is generally greater than 5 microns and veryheterogeneous. The stability on storage and the breaking of this type ofemulsion are found to be difficult to control and the surfacingsresulting therefrom are not sufficiently homogeneous. It is clear thatthis can be detrimental as regards the use of the emulsions and thefinal mechanical quality of the corresponding surfacings.

One subject of the present invention (is, specifically, to propose aprocess for preparing emulsions which are concentrated in a highlyviscous phase such as bitumen and are also calibrated.

In particular, the invention is based on the demonstration that thedirect mixing of a highly viscous phase, i.e. a phase which has aviscosity of between 1 and 5000 Pa.s at the time of emulsification, witha phase which is immiscible therewith, in the presence of a surfactant,leads, under low shear and in a very short space of time, to aviscoelastic paste which is advantageously found to have thespecificities of an emulsion.

More specifically, the emulsification method according to the inventionis novel in that it makes it possible to manufacture highly concentratedemulsions of “water-in-oil” or “oil-in-water” type by directly mixingtogether the two phases in a laminar shear regime. It thus differsclearly from conventional emulsification processes, such as the onementioned above, which operate in a turbulent regime. It also differsfrom the conventional techniques of emulsification in a laminar regimewhich proceed by gradual incorporation of a first phase to be emulsifiedinto a second phase, or vice versa.

A first subject of the present invention is thus a process which isuseful for emulsifying a first hydrophobic or hydrophilic phase with aviscosity of between 1 and 5000 Pa.s or more with a second phase whichis immiscible with the said first phase, characterized in that itinvolves:

where necessary, a pretreatment of the said first phase to be emulsifiedso as to adjust its viscosity to a value of less than 5000 Pa.s,

the addition, in a single portion, of the said phase to a second phasewhich is immiscible with the said first phase, in the presence of atleast one surfactant, and

mixing them together under a laminar shear regime until a stableemulsion is obtained in which the said first phase is present in aproportion of from 75 to 95% by weight.

The emulsion obtained after the process claimed has the appearance of aviscoelastic paste. Advantageously, it is found to be redispersibledespite a high concentration of one of its phases. It can thus bediluted so as to adapt the concentration of the final emulsion to therequirements of the application envisaged.

Besides a high concentration of one of its phases, the emulsion obtainedaccording to the invention has a very narrow particle-size distributionand the average diameter of its droplets can be readily controlled bymeans of the shear rate or by means of the formulation parameters andmore particularly the concentration of the second phase, also known asthe diluent phase.

In this regard, a subject of the present invention is also a processwhich is useful for preparing an emulsion with a concentrated andcalibrated hydrophobic or hydrophilic phase and with a viscosity ofbetween 1 and 5000 Pa.s or more, comprising

where necessary, a pretreatment of the said phase to be emulsified so asto adjust its viscosity to a value of less than 5000 Pa.s,

the addition, in a single portion, of the said phase to a second phase,which is immiscible with the said first phase, in the presence of atleast one surfactant, and

mixing them together under a laminar shear regime until a stableemulsion is obtained in which the said first phase is present in aproportion of from 75 to 95% by weight, characterized in that the sizeof the droplets in the said first phase is controlled in the saidemulsion by adjusting the concentration in the second phase for a givenshear rate and a given surfactant concentration.

As a general rule, the size of the droplets in the first phase decreaseswhen the shear rate and/or the concentration of surfactant increase. Theinventors have thus demonstrated, unexpectedly, that it is possible toadjust the size of the droplets in the first phase by controlling theamount of the second phase introduced to prepare the emulsion. The sizeof the droplets does not change monotonically with the amount of thesecond phase: the size first decreases and then increases when theamount of the second phase increases.

According to this specific mode of the invention, it is thus found to bepossible to obtain an emulsion with a minimum average droplet diameter,i.e. about 2 microns or even less, for an optimum amount of this secondphase. The assessment of this critical volume of the second phase infact depends on the chemical nature of the said first viscous phase tobe emulsified. For a given amount of the first phase to be emulsified,the change (for a fixed stirring speed) of the average diameter of thedroplets, obtained during its emulsification, is established forvariable amounts of second phase. The critical volume is the volume forwhich the diameter of the droplets is a minimum. Needless to say, thisassessment of the critical volume is made for a given shear rate and agiven surfactant concentration.

Preferably, the emulsion has an average droplet diameter of less than 2microns, i.e. a relatively smaller size than that obtained according toconventional emulsification processes. As regards the polydispersity, itis less than 40%, as compared with, for example, more than 100% forconventional bitumen emulsions. This polydispersity is expressedaccording to the Laser Coulter LS 230 granulometer and corresponds tothe standard deviation of the distribution divided by the averagediameter obtained (Coulter LS 230 documentation, page B-5).

The shear applied to the mixture is a laminar shear and is thus adjustedsuch that the stirring spindle rotates at low speed. This regime ischaracterized in that it has a low Reynolds number.

In fluid mechanics, the flow regimes are generally characterized withreference to a dimensionless number known as the Reynolds number, whichis defined by Re=ρνL/η, in which

ρ is the average density,

ν is the flow rate, which can be likened in the case of the presentinvention to the speed of the stirring spindle,

L is a characteristic length which can be likened in the process claimedto the gap between the stirring spindle and the wall of the reactor, and

η is the average viscosity of the emulsion.

For the purposes of the invention, the laminar regime is characterizedin that it has a low Reynolds number, of less than about 1000. Beyondthis value, the regime becomes turbulent.

As an illustration, if values of ρ of 1000 kg/m³, ν of 0.3 ms⁻¹(circumferential speed of a spindle with a radius of 5 cm rotating at aspeed of 500 rpm), L of 0.002 m and η of 10 Pa.s (characteristicviscosity, at the shear rate applied, of an emulsion in which one of thephases is present in a proportion of 90% by weight) are considered inthe process claimed, this gives a Reynolds number Re of 0.06, whichclearly shows that the shear regime applied to the emulsions is laminar.

In the case of a conventional process carried out in an industrialreactor, using values of ρ of 1000 kg/m³, ν of 30 ms⁻¹ (circumferentialspeed of a cylinder with a radius of 0.5 m rotating at a speed of 5000rpm), L of 0.001 m and η of 10⁻² Pa.s (characteristic viscosity, at theshear rate applied, of an emulsion in which one of the phases is presentin a proportion of 60% by weight), then a Reynolds number Re of 3000 isinstead found, corresponding to a turbulent regime.

Preferably, the stirring speed ranges between 100 and 1000 rpm(corresponding to a shear rate of between about 250 and 2500 s⁻¹) and ismore preferably from about 400 to 500 rpm (corresponding to a shear rateof about 1000 s⁻¹). It is adapted so as to convert very rapidly, i.e.within a period of a few seconds to a few tens of seconds, the mixtureinto the expected emulsion.

To this end, the stirring system is chosen so as to ensure bothhomogenization and shear of the mixture. Thus, stirrers such as flexiblegrates, propellers or paddle stirrers are particularly suitable in thecontext of the present invention.

Preferably, the emulsification is carried out at ambient temperature andpressure. However, certain compounds whose viscosity is greater than5000 Pa.s should preferably be treated by heating so as to reduce theirviscosity. In order to avoid boiling of the second phase, under theeffect of the heat supplied by the preheated viscous first phase, it maybe necessary to work at a pressure above atmospheric pressure. Theoptimum temperature and pressure conditions will be determined by aperson skilled in the art by means of simple routine operations.

For the purposes of the invention, the said first hydrophobic orhydrophilic phase is or comprises at least one hydrophobic orhydrophilic compound. For example, it may comprise a mixture of severalcompounds of either hydrophilic or hydrophobic nature and in diluted orundiluted form.

This hydrophobic or hydrophilic phase is characterized in all cases by avery high viscosity, from about 1 to 5000 Pa.s or more. It has theappearance of a highly viscous fluid, and is thus particularly difficultto emulsify.

As an illustration of compounds which can be dispersed according to theinvention, mention may be made most particularly of hydrophobicmaterials such as, in particular, colophony esters (adhesives industry),lanolin (cosmetics), bitumens, waxes (cosmetics, cleaning products,etc.), polybutadienes of low molecular mass, or hydrophilic compoundssuch as, in particular, polyethylene glycols, sugars, gelatins(agar-agar, carrageenans, etc.) (pharmaceutical and food industries) andmixtures thereof.

Since some of the corresponding hydrophobic or hydrophilic phases have ahigh viscosity at room temperature, in particular of greater than 5000Pa.s, it is found to be necessary to lower their viscosity to a valuebelow 5000 Pa.s in order to give them beforehand a fluidity which issuitable for their subsequent mixing with the said second phase. Asexplained above, the said first phase can then be subjected to apretreatment which preferably consists of a heating operation combined,where necessary, with mechanical stirring (faster homogenization of thetemperature in the viscous phase). In point of fact, this heating isfound to be more particularly necessary when the said first phase has aviscosity at room temperature such that its flow and/or pumping isimpeded. In this regard, any destabilization of the emulsion obtained,liable to be brought about by the evaporation of the second phase,should be prevented. In this specific case, the viscoelastic pasteobtained may be diluted in the hours following its preparation andpreferably immediately after it has been prepared, so as to limit theinstabilities (coalescence) which may result from the evaporation.

As regards the second phase, it can be either aqueous or oily. When itis an oil, this oil can be, without preference, a mineral, plant oranimal oil. Mineral oils which may be proposed in particular areparaffinic oils and naphthenic oils or mixtures thereof.

The surfactants used according to the invention can be chosen from anycategory of surfactant (anionic, cationic, nonionic, amphoteric, etc.surfactants). They can be chosen from the surfactants conventionallyused in processes for emulsifying the said first phase underconsideration. Needless to say, they are selected taking into accountthe type of emulsion, viscous hydrophobic phase in aqueous phase orviscous hydrophilic phase in oily phase, which it is envisaged toprepare according to the invention. Thus, in order to obtain emulsionsof water-in-oil type, surfactants with a hydrophilic/lipophilic balance(HLB) of less than 7 are selected, and for emulsions of oil-in-watertype, surfactants with an HLB of greater than 14 are selected.

The term “HLB” (Hydrophilic-Lipophilic Balance) denotes the ratio of thehydrophilicity of the polar groups of the surfactant molecules to thehydrophobicity of the lipophilic part of these same molecules; this is aterm commonly used in the surfactants field (see the treatise“Techniques de l'Ingénieur [Engineering Techniques]”, chapter A7610:“Les agents de surface [Surfactants]”).

Advantageously, care will be taken to predissolve the surfactants in thesecond phase in order to avoid any problems of dissolution kinetics. Thesurfactants are used in the process according to the invention in areduced amount preferably ranging between 0.5% and 5% by weightexpressed relative to the weight of the said first hydrophobic orhydrophilic phase to be emulsified, so as to extract the maximum valuefrom the amount of surfactant. The surfactant yield is defined as beingthe ratio of the amount of surfactant required to cover the disperseddroplets to the total amount of surfactant used.

The process according to the invention is most particularly useful forpreparing aqueous bitumen emulsions.

Thus, starting with 100 grams of bitumen and for a water concentrationof 5 grams per 100 grams of bitumen, highly concentrated emulsions, i.e.containing 95% by weight of bitumen, which can be diluted and which arestable on storage can be prepared.

As mentioned above, the viscoelastic paste obtained may be diluted withhot water (60° C.) in the hours following its preparation, andpreferably immediately after it has been prepared. Emulsions having,after dilution, a bitumen concentration of between 75% and 85% are foundto be particularly stable for at least several months.

The introduction of a surfactant such as, in particular,tetradecyltrimethylammonium bromide in a proportion of 1.5 grams per 100grams of bitumen also allows the size of the droplets in the emulsion tobe reduced to a value in the region of 1 micron.

One specific embodiment of the invention is thus directed towards theuse of the process claimed for the preparation of a concentrated andcalibrated bitumen emulsion. This process comprises the steps consistingin heating bitumen to a temperature of 95° C., mixing it, in a reactorand at atmospheric pressure, with 5% by weight of water and 0.5% to 1.5%by weight of a surfactant relative to the weight of the bitumen, andapplying a shear rate to the said mixture thus obtained so as to formthe said emulsion, which is recovered.

As regards the stirring speed, this can range between 0 and 1000 rpm andis preferably from about 400 to 500 rpm, which corresponds to a shearrate of about 1000 s⁻¹. A concentrated bitumen emulsion is obtained veryquickly, i.e. in a few seconds, under the effect of this shear. Thisemulsion has the appearance of a non-emulsified viscoelastic paste. Anexamination of this emulsion shows that it has a bitumen concentrationwhich can be up to 90 or even 95% by weight. Advantageously, this pasteis found to be fully redispersible in water despite its high bitumenconcentration.

A subject of the present invention is also bitumen emulsions,characterized in that they have a bitumen concentration of greater than75% and preferably at least equal to 85% by weight of bitumen.

Preferably, the bitumen emulsions claimed and obtained according to theprocess of the invention have a polydispersity of about 40%. Theyconsist of droplets with an average diameter of less than or about 2microns, and preferably less than 1 micron.

It is clear that the process according to the invention, and likewisethe emulsions thus obtained, are particularly advantageous in the roadindustry. The process claimed makes it possible to prepare highlyconcentrated fine bitumen emulsions with very good control of the finalsize of their droplets, by a fast, simple protocol with a small amountof surfactants.

The present invention also extends to emulsions of hydrophobic orhydrophilic phase, obtained according to the process claimed. It is thusfound to be most particularly useful for preparing concentrated andcalibrated emulsions of therapeutic, cosmetic or food-use interest.

The examples and figures given below, without any limitation of thepresent invention, demonstrate other advantages thereof.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1: Graph representing the change in the average diameter of thedroplets obtained for a stirring speed of about 400 rpm (shear rate ofabout 1000 s⁻¹) as a function of the amounts of water and surfactant(TTAB) present at the start.

FIG. 2: Graph representing the change in the average diameter ofdroplets prepared according to Example 3 as a function of the shear rateapplied during the emulsification.

FIG. 3: Graph representing the change in the average diameter of thedroplets obtained for a stirring speed of about 400 rpm (shear rate ofabout 1000 s⁻¹) as a function of the amount of TTAB.

FIG. 4: Graph of efficacy of the emulsification obtained for a stirringspeed of about 400 rpm (shear rate of about 1000 s⁻¹), mass of TTABused/mass introduced.

FIG. 5: Graph representing the change in the average diameter of thedroplets as a function of the amounts of oil, for an emulsificationcarried out according to Example 5.

FIG. 6: Microscope photograph of a PEG emulsion obtained according toExample 5.

FIG. 7: Graph representing the change in the average diameter of thedroplets as a function of the amount of Span 80® or an emulsion preparedaccording to Example 5.

FIG. 8: Comparison in terms of polydispersity of an emulsion accordingto the invention and of a control emulsion (Example 7).

EXAMPLE 1 Protocol for Preparing an Aqueous Bitumen Emulsion Accordingto the Invention

100 grams of bitumen with a penetration index of 90/100* are heated to atemperature of about 100° C. An aqueous tetradecyltrimethylammoniumbromide (TTAB) solution of variable concentration is prepared. Theheated bitumen is poured onto the aqueous solution and the mixture isblended for a few seconds using a flexible grate, at 400 rpm (1000 s⁻¹)in a reactor 10 centimetres in diameter. The emulsion obtained almostinstantaneously is characterized in terms of droplet diameter.

*The penetration index is a parameter used in the road industry tocharacterize the “hardness” of a bitumen at 25° C. The process formeasuring the penetration index is governed by ASTM (American Societyfor Testing and Materials) standard D5-86.

A commercial Laser Coulter LS 230 granulometer (from the companyCoultronics) is used to measure the diameter of the droplets.

EXAMPLE 2 Effect of the Amount of Water and of Surfactant (TTAB) on theAverage Diameter of the Droplets in a Bitumen Emulsion at Constant Shear

The protocol described in Example 1 is repeated for two TTABconcentrations, 0.75 grams and 1.5 grams, and in the presence of anamount of water ranging between 4 and 14 grams for each of theseconcentrations. The emulsions obtained after each of the tests arecharacterized by the average diameter of their droplets. The results aregiven on the graph in FIG. 1.

The finest emulsion is obtained for a constant amount of water of about5 grams per 100 grams of bitumen. The minimum droplet size thus obtainedcan also be reduced by increasing the amount of surfactant. Thus, for1.5 grams of TTAB in 5.5 grams of water, the minimum diameter is reducedto 0.8 microns, as against 2 microns with 0.75 grams of TTAB.

EXAMPLE 3 Effect of the Shear Rate on the Average Diameter of theDroplets in the Emulsified Viscous Phase

The protocol described in Example 1 is repeated with 100 g of bitumen,1.5 g of TTAB and 5.5 g of water for variable stirring speeds. Theemulsions obtained after each of the tests are characterized by theaverage diameter of their droplets. The results are represented on thegraph in FIG. 2. It is thus observed that a high shear rate promotes theformation of droplets of markedly smaller average diameter. However, thestirring speed should not exceed a threshold value of 1000 rpm (about2500 s⁻¹), above which the excessively violent shear destroys theconcentrated emulsion.

EXAMPLE 4 Effect of the Amount of Cationic Surfactant on the AverageDiameter of the Droplets of a Bitumen Emulsion with a Constant Volume ofWater and at Constant Shear

The protocol described in Example 1 is repeated for different TTABconcentrations, in the presence of 5.5 grams of water. The resultsobtained are represented on the graph in FIG. 3.

It is noted that 1 gram of TTAB per 100 grams of bitumen is sufficientto achieve sizes of the order of one micron.

A characterization of the yield for the processes as a function of themass of TTAB introduced shows in fact that the maximum efficacy isvirtually achieved for this maximum amount of TTAB. More specifically,this result is obtained by taking the yield as being the ratio of themass of surfactants present at the interfaces, to the total mass ofsurfactants introduced. The mass of surfactants present at theinterfaces is determined simply by measuring the residual amount ofsurfactants present in the second phase after a controlled dilution. Thegraph in FIG. 4 represents this ratio as a function of the total massintroduced into the 5.5 grams of water required to emulsify 100 grams ofbitumen.

EXAMPLE 5

Assessment of the Optimal Amount of Second Phase Relative to the AverageDiameter of the Droplets of an Emulsion

In this example, the viscous hydrophilic phase to be dispersed is anaqueous mixture containing 44% polyethylene glycol PEG 35000, thesurfactant is Span 80® (sorbitan monooleate sold by Sigma), present in aproportion of 1.5 g per 100 g of the phase to be dispersed, and thecontinuous phase is dodecane.

Several mixtures of these compounds are prepared for different amountsof dodecane at a shear of 400 rpm (1000 s⁻¹) (the apparatus is the sameas that used for the manufacture of the bitumen emulsions) in a reactor.The emulsions, obtained almost instantaneously, are characterized by theaverage diameter of their droplets. The results are given on the graphin FIG. 5. The photograph given in FIG. 6 is a microscope photograph ofone of these emulsions.

It is seen on the graph in FIG. 5 that the minimum diameter, i.e. about2 microns, is obtained for 3 g of dodecane.

EXAMPLE 6 Effect of the Amount of Surfactant on the Average Diameter ofthe Droplets of an Emulsion at Constant Shear

The protocol described in Example 5 is reproduced for severalconcentrations of Span 80® surfactant and 3 g of dodecane. The emulsionsobtained after each of the tests are characterized by the averagediameter of their droplets. The results are represented on the graph inFIG. 7.

The finest emulsion is obtained for 4 g of Span 80®.

EXAMPLE 7 Comparison of a Bitumen Emulsion According to the Inventionand of a Conventional Emulsion in Terms of Polydispersity and AverageDroplet Diameter

The industrial technique used consists in injecting, under pressure(about 1.5 atmospheres) and at 130° C., bitumen, on the one hand, andthe aqueous soapy phase, on the other hand, between two coaxial rollers(a rotor and a stator) spaced about 1 mm apart. The rotor rotates at aspeed of about 5000 rpm. The emulsification takes place directly in the1 mm gap, and does so in a turbulent regime. The fraction by volume ofthe phase to be dispersed cannot exceed 70% or else it will block thesystem.

This assessment is carried out using an emulsion obtained in accordancewith the present invention and incorporating 0.75 grams of TTAB per 5.5grams of water and 100 grams of bitumen and of a conventional industrialbitumen emulsion. This industrial emulsion contains 60 grams of bitumen,0.5 gram of cationic surfactant and 39.5 g of water.

The granulometric distributions obtained by the two techniques arepresented in FIG. 8.

For the emulsion according to the invention, an average size centred atabout 2 microns is observed, with a polydispersity in the region of 30%.In turn, the control emulsion has a markedly larger average dropletdiameter, i.e. 5 microns, and a polydispersity not in accordance withthe invention, i.e. markedly greater than 40%.

What is claimed is:
 1. Process for emulsifying a first hydrophobic orhydrophilic phase having a viscosity between 1 and 5000 Pa.s with asecond phase immiscible in the first phase, comprising: combining thefirst phase in a single portion with the second phase, and at least onesurfactant, and mixing the first phase, second phase, and surfactanttogether under a laminar shear regime to obtain a stable emulsion havingan average droplet diameter less than 2 microns and a polydispersityless than 40%, the first phase being present in a proportion of 75 to95% by weight.
 2. Process according to claim 1, characterized in thatthe first phase is obtained by adjusting phase viscosity from more than5000 Pa.s. to less than 5000 Pa.s.
 3. Processing according to claim 1,characterized in that the second phase is present in an amount such thatthe average droplet diameter of the emulsion is less than. or equal to 1micron.
 4. Process according to claim 1, characterized in that thesurfactant is present in an amount between 0.5% and 5% by weight,relative to the weight of the first phase.
 5. Process according to claim1, characterized in that the first phase comprises at least one compoundselected from the group consisting of bitumens, colophony esters,polybutadienes of low molecular mass, waxes, lanolin, sugars,polyethylene glycols, gelatins, and mixtures thereof.
 6. Processaccording to claim 1, characterized in that the laminar shear regime hasa Reynolds number less than
 1000. 7. Process according to claim 1,characterized in that laminar shear regime has a shear rate rangingbetween 250 and 2500 s⁻¹.
 8. Process according to claim 1, wherein theshear rate is about 1000 s⁻¹.
 9. Process according to claim 1,characterized in that the first phase is a bitumen phase and the secondphase is water.
 10. Process for preparing a concentrated and calibratedemulsion using a hydrophobic or hydrophilic phase having a viscositybetween 1 and 5000 Pa.s, comprising: combining, in a single portion as afirst phase, the hydrophobic or hydrophilic phase having a viscosityless than 5000 Pa.s with a second phase immiscible in the first phase,and at least one surfactant and mixing the first phase, second phase,and surfactant together under a laminar shear regime, having a shearrate, to obtain a stable emulsion having an average droplet diameterless than 2 microns and a polydispersity less than 40%, the first phasebeing present in a proportion of 75 to 95% by weight, wherein theaverage droplet diameter less than 2 microns is obtained by adjustingthe concentration of the second phase based on the shear rate andsurfactant concentration.
 11. Process according to claim 10,characterized in that the hydrophobic or hydrophilic phase is obtainedby adjusting phase viscosity from more than 5000 Pa.s to less than 5000Pa.s.
 12. Process according to claim 10, characterized in that thesecond phase is present in an amount such that the average dropletdiameter of the emulsion is less than or equal to 1 micron.
 13. Processaccording to claim 10, characterized that the surfactant is present inan amount between 0.5% and 5% by weight, relative to the weight of thefirst phase.
 14. Process according to claim 10, characterized in thatthe first phase comprises at least one compound selected from the groupconsisting of bitumens, colophony esters, polybutadienes of lowmolecular mass, waxes, lanolin, sugars, polyethylene glycols, gelatins,and mixtures thereof.
 15. Process according to claim 10, characterizedin that the laminar shear regime has a Reynolds number less than about1000.
 16. Process according to claim 10, characterized in that thelaminar shear regime has a shear rate ranging between 250 and 2500 s⁻¹.17. Process according to claim 16, wherein the shear rate is about 1000s⁻¹.
 18. Process according to claim 10, characterized in that the firstphase is a bitumen phase and the second phase is water.
 19. Processaccording to claim 10, wherein the concentrated and calibrated emulsionis prepared as a concentrated and calibrated bitumen emulsion. 20.Process for preparing a calibrated and concentrated bitumen emulsion,comprising: heating the bitumen to a temperature of 95° C., mixing, in areactor under a laminar shear regime and at atmospheric pressure, theheated bitumen with water at 5% by weight relative to the weight ofbitumen and a surfactant at 0.5 to 1.5% by weight relative to the weightof bitumen, to form a bitumen emulsion having a polydispersity of lessthan 40% and an average droplet diameter less than 2 microns. 21.Process according to claim 20, characterized in that the bitumenemulsion is at least 90% bitumen, by weight.
 22. Process according toclaim 21, wherein the bitumen emulsion is about 95% bitumen, by weight.